Thread cutter



B. BECKER.

THREAD CUTTER. APPLICATION FILED SEPT. 6, I918.

L422A07; Patented July 11, 1922;

WITNESSES INVENTOR RUDOLPH BECKER, O35 ROSELLE- NEW JERSEY, ASSIGNOR TOTI-IE SING-ER, MANUFACTURING COMPANY, A CORPORATION O1 NEW JERSEY.

Specification of Letters Patent.

Patented July it, ft, 192.2.

Application filed. September 6, 1918. Serial No. 252,938.

To all whom it may concern:

Be it known that I, RUDOLPH BECKER, a citizen of the United States,residing at Roselle Park, in the county of Union and State of NewJersey, have invented certain new and useful Improvements in ThreadCutters, of which the following is a specifioation, reference being hadtherein to the accompanying drawings.

This invention relates to an improvement in thread-cutting means forsewing-machines.

The objects of the invention are to provide a simple and efficientthread-cutter operating with a shearing action, and to provide meansthereon for guiding one limb' of a thread-loop within the jaws of theshears.

The thread-cutter in the embodiment shown is located in the work-arm ofthe machine and comprises a shear blade pivot-ally connected to thework-arm, a second shear blade having a floating pivot, a pivotalconnection between the blades, means carried by one of the blades forseizing the needleloop and deflecting one limb thereof into the onsubstantially the line 4.4L of Fig. 3, the

blade 8 being shown in elevation.

In the drawings 1 is the machine base having a forwardly projectingwork-arm 2 and overhanging arm 3, the latter carrying the usualneedle-bar having'a needle 4. Pivotally mounted at 5 in the work-arm 2adjacent the 'looper 4c is a member in the formof a bellcrank-lever, onearm 6 of which forms one of the shear blades of the cutter, the otherarm 6' being connected to an operating link 7. A second shear blade 8has a pivotal connection at a point 8' intermediate its ends with aspring wire or other link 9, the latter being bent downwardly andsecured to the side-wall of the work-arm by a screw or other means 9 asshown in Fig. 4. The blade 8 also has a pivotal connection at 10 withblade 6. The back edge of blade 8, or the edge opposed to its cuttingedge, has a cam surface at 8, adapted to engage with a straight portionor abutment 8 on the inner wall of the work-arm as the blade moves onits pivot 10. The spring wire link 9, in ad dition to serving as afloating fulcrum for the blade 8, forms a yielding means for holding thecam-surface 8 against the surface 8 thus opening the blades when blade 6is re tracted, and bears downwardly against the blade 8 to therebymaintain'the cutting edges of the blades always in contact. It will benoticed that the blade 6 has a fined pivot, while the blade 8 has afloating one, and a toggle is formed between the pivot point 5 of blade6, the bearing point of cam 8 on surface 8 and the point of connectionof the blades at 10. Extending laterally from the end of blade 6 is aprojection or nose 1.1, which acts to enter a threaddoop held by thelooper and to deflect and detain one limb thereof for severance by theblades. The operating link 7 may be actuated in any desired man ner, andin the embodiment shown is connected to a stop-motion mechanismsubstantiall the same asthat shown in the patent to M. Horton, No.1,051,998, dated F ebruary 4c 1913. It is obvious, however, that theactuating means for closing the blades may be applied in many ways andto either blade.

At predetermined periods in the operation of the machine abellcrank-lever 12 (Fig.2) at the lower end of the stop-motion mechanismis moved to actuate link '7 against the tension of a spring 13. Thiscauses the bellcrank-lever 6, 6 to move on its pivot 5 and through thepivotal connection 10 and the bearing of the cam 8 onsurface 8, blade 8is oscillated about said pivot 10. This causes a relative closingmovement of the two shearblades and asthe thread is caught between themit is severed. It will be noticed that as blade'6 moves toward thesurface 8 the bearing point of the curved surface of the cam 8 on thissurface 8 moves nearer the pivot 10 thus shortenlng its leverage andacceleratmg the relative movements of the two blades. This gives acomparatively slow of the cutting edges similar to a chopping movementthus givlng a more reliable opera tion. Because of this movement of theblade 8 given by the cam, the cutting edge is moved away from thesurface 8 sufiiciently to cut the thread when it is substantially inline with the needle opening, but when theblades are opened the cuttingedge of blade 8 is'retracted out of the line of the needle opening andso will not interfere with the thread or needle, as clearly shown inFig, 3. The cam surface 8 and the abutment 8 may be dis pensed with ifdesired in which event the spring 9.wouldform a yielding means forclosing the shear-blades to cut the. thread upon operation of the blade6 instead of the positive means obtained with the use of cam 8 andabutment surface 8 In the movement of blade 6 the projectionv 11 haspreviously enteredthe thread-loop leading as usual from the looper anddeflected and detained one, limb of thesame, which limb is severed bythe-closing ofblades (Sand 8.

Having thus set forth the nature of the invention, what I claim hereinis:

1. In a sewing machine, a thread-cutter comprising a cutting bladehaving, a fixed fulcrum, a secondcutting blade having a floating fulcrumand-a cam-surface, a pivotal connection between-saidfblades separatefrom the floating fulcrum, means for actuatinggone of said blades, andmeans. coacting: withthe cam-surface for swinging the other blade aboutthe pivotal connection between the blades.

2. In a sewing machine, a thread-cutter comprising a cutting bladehaving a fixed fulcrum, a second cutting blade coacting therewith havinga floating fulcrum and a came-surface, a pivotal connection; betweensaidyblades intermediate their fulcrums, means for moving said firstblade on its fulcrum, and, means coacting; with the camsurface to movethe second blade about the pivotal connection between the blades.

3. In a sewing machine, a work-support, stitch-forming mechanismincluding a re ciprocating needle and a.complemental1looptaker, afulcrumed cutting blade, a second fulcrumed cutting blade coacting withsaid first mentioned blade and having a link connection withthemachine,,one of said blades having. a portion so formed: and positionedas to venter between the limbs Of'a needleloop below the work-support,apivotal connection between said bladesintermediate their fulcra, andmeans for actuating said blades.

4. In a sewing machine having stitchforming mechanism and a stop-motionmechanism therefor,v a cutting blade pivotally mounted on the machine,a. second; cutting blade having a link connection with the machine and apivotal connection with said first blade, and means operated by thestopmotion mechanism for actuating said blades.

5. In a sewing machine, a thread cutter comprising a pair of pivotallyconnected shear blades, yielding means for maintaining the cut-tingedges of said bladesin contact, said means forming a fulcrum for one ofsaid blades separate from the pivoted connection between the blades, andmeans for actuating said blades; 7

6. In a thread-cutter, a pivotally mounted slieai blacle, means forvmoving it about its pivot, a second shear-blade pivoted to thelirstmentioned shear-blade at a. point spaced from the first mentioned pivot,a cam ens-aid second shear-blade, and a fixed abutment against whichsaid cam reacts; as a fulcrum during the movement of the first mentionedblade.

7. In a sewing machine, a threadcutter com risin a blade havin i a fixedfulcrum a second blade pivoted tothe first blade intermediate itscuttingedge and its fulcrum,

the second blade being provided with a cam,

means on the machine cooperating with the cam, yielding means providinga floating fulcrum for the second blade and; acting to retain the camagainst its cooperating means, and means for operating one of theblades8. In a sewing machine, a threadrcutter comprising a pair of pivotallyconnected sheaiyblades, one blade being pivoted to stitch-formingmechanism including a. re-

ciprocatingneedle andiacomplemental looptaker, andcooperatmgshear-blades mounted on the same side oftheworl: as'the loop;

taker, one of said blades being formed with a loop -dividing point whichis so positioned as to be projected duringthe closingmovement of saidblades into the last needle-loop whileheldspread by the loop-taker.

Inxtestimony whereof, I have signed my name tolthis specification.

,snnoLrl-i BECKER.

